In the past, various materials have been used to form building materials such as molded panels. Initially, polyurethane and isocyanurate foamed plastics, both petroleum derivatives, were used to manufacture molded panels. Such panels were light weight, low cost, and thermally efficient. The components were readily available and could be easily transported. When the basic ingredients were combined, they expanded to approximately twenty times their original volume encapsulating myriads of minute gas bubbles. Initially, such panels were susceptible to slight shrinkage during set and cure stages. Such problems were later overcome. However, a controversy arose within the construction industry concerning the use of foam plastics in buildings. It was discovered that under certain conditions of heat and/or fire, the materials burned. The gases emitted were toxic. Under high heat with a spark, those gases could flash or explode. Additionally, since 1973, the subsequent ever upward spiraling cost of petroleum products further decreased the desirability of these foamed plastics as building components.
After a two year indepth analysis, it was determined by consent agreement between the Federal Trade Commission and the Society of Plastics Industry that foamed plastics could be used in buildings if they were totally encapsulated within fire resistive, nontoxic materials. Such materials were formed by encapsulating the foamed plastics in a variety of inorganic products such as a rigid homogenous foamed glass product manufactured by Pittsburgh Corning Corporation and marketed under the trademark "FOAMGLAS".
The U.S. Pat. No. 4,419,133 to Shubow et al, issued Dec. 6, 1983, discloses a bonded aggregate structure for making moldable rigid insulation. The Shubow et al patent discloses a bonded aggregate structure made from a mixture of magnesium oxide, aluminum oxide, aggregate, and mono aluminum phosphate acidic solution. The aggregates disclosed are cellular, low density aggregates selected from the group including inorganic materials such as glass beads, perlite, vermiculite, and stone or other refractory aggregates.
Further development has proceeded in search of methods of producing bonded composite structures at lower costs. Such structures must be of low cost but must also withstand high temperatures. The instant invention provides a low cost bonded composite structure wherein the binders are blended or mixed with a fibrous cellulose filler which is essentially a waste product that produces results similar to those achieved with the use of inorganic, insulating-type aggregates but at a much lower cost. Such organic materials would normally be highly flammable. Unexpectedly, however, pursuant to the subject invention, such cellulose filler materials do not burn and form rigid bonded structures able to withstand temperatures in excess of 3000.degree. F.